Even more answers
"This article says that many popular oils, such as Watco and other “Danish” oils, are really just blends of varnish and an oil.
http://www.popularwoodworking.com/features/finish2.html
Another article specifically says Watco is linseed and varnish."
As I mentioned previously, most “oil finish” products are blends. They typically mostly thinner, blended with varnish and in some cases linseed or tung oil. The only way to know that you’re actually applying an oil finish is to use pure oils.
"The linked article and others I have seen, along with one paddle maker, say pure tung is very difficult to use. It must be sanded vigorously after every application and many, many coats must be used.
That’s complete BS. Tung oil is incredibly easy to use as a finish, as is boiled linseed oil. You wipe it on, let it penetrate, then wipe it off. Each succeeding coat helps fill the pores in the wood, but it won’t build to any appreciable thickness. Perhaps that’s the issue with the author of the article, he’s trying to create a varnish like finish with tung oil, which is a complete waste of time and a poor application for it. As with any finishing product, you have to understand it and use it where it’s appropriate. Lack of understanding is where most finishing myths come from.
BTW, for finishing paddles, I’ve found that there’s no point in applying more than 4 or 5 coats of oil or oil/varnish blend and as few as 3 will do the trick.
“Most of the articles say oil has no UV protecting qualities. Some say it should be applied over bare wood with nothing underneath it.”
Correct on both counts.
“If any of these are correct, it would seem that if you are going to apply oil, you shouldn’t apply an epoxy sealer first. The epoxy will interfere with the saturation and polymerization of the oil, and the epoxy won’t be protected from UV by the oil.”
Correct again, except that the epoxy shouldn’t affect the polymerization of the oil, since all that’s required for that is oxygen.
“What the heck happens to epoxy anyway if it isn’t UV protected? Something horrific?”
It breaks downs and gets chalky, losing all of its strength in the process. If it’s used as a wipe on/wipe off coating on wood (applied like oil), it is somewhat protected by the wood itself. If it’s applied as a film coating (applied like varnish), it’s unprotected and subject to degradation. Depending on how much you use your paddle and how you store it, the damage could take anywhere from months to years to become bad enough to raise concerns.
“I’m more interested in protecting the wood than the epoxy. Does wood itself need UV protection?”
In general, no, as wood is not damaged by UV. Some - perhaps most - woods change color due to UV exposure. Pine turns orange, purple heart turns brown, etc. If the color change is undesirable, a UV protectant will slow the change, but I don’t know if it’s possible to completely eliminate it.
“My investigations this summer have not changed my longstanding subjective preference for the feel of oiled grips over varnished grips. But now I wonder certain things. Should I oil the whole shaft? If I do, shouldn’t I forbid an epoxy “sealant” underneath it? But, confusingly, if the oils I’m using are really half varnish anyway, maybe I’m back to voodoo and have always been fooling myself about “oil”.”
That’s one of the biggest problems with wood finishing, the huge amount of misinformation foisted on the public by finish manufacturers. Calling a wiping varnish an “Oil Finish” is confusing to the consumer and just plain wrong.
To answer your question, if you like the look and feel of oil finishes, either use pure oil or make your own oil/varnish blend. Unless you have a specific need for epoxy, there’s no point in using it. As I mentioned, I epoxy coat the tips of my paddles for durability and use an oil varnish blend on the rest of the paddle. It gives me the look and feel I like with better durability that just oiling the entire paddle. You may prefer a different approach. Now that you understand what these products are and how they work, you can figure out what’s the optimum finish for your needs.
“Oh, on top of all this, other articles say that “oil” or “varnish” are preferred or not for finishing depending on what kind of wood is being used. Cherry is different from oak. Something to do with pore sizes.”
Again, it depends on the application. What you use on furniture or cabinets may not the the ideal finish for a paddle. It also depends on what one is trying to achieve with the finish. Blanket statements like that simply cannot be correct for every application. You need to know the goals of the author and the materials being used.
“http://74.125.93.132/search?q=cache%3AUkxpObvIAPUJ%3Awww.woodcentral.com%2Fbparticles%2Foil_finishes.pdf+watco+oil&hl=en&gl=us”
In this case, the author apparently doesn’t know what he’s using. Because Watco contains varnish, it can be built up slowly by using many thin coats. He also doesn’t seem to realize that the sanding he’s doing is filling in the pores and knocking down the high spots, which is what ultimately produces a fine finish. I routinely apply the last two coats of finish on my paddles using 400 and 600 grit sandpaper. Even on cedar, the results are impressive.
“I guess I forgot my botany. I thought wood was a closed cell structure.”
Yes and no. There are closed cells, but there are also tubular structures. This varies greatly between various species of wood. Sawing/planing/scraping/sanding opens some cells and tubes, which will then absorb a finish. Sanding plows furrows in the wood, which will also hold finishes. It’s a whole 'nuther world at that level.